#! /usr/local/bin/python3

import time

class Timer:
    def __enter__(self):
        self.start = time.time()
        return self
    def __exit__(self, a, b, c):
        self.stop = time.time()
        diff = self.stop - self.start
        print(f'Elapsed time: {diff} secs')

def make_tarai():
    cache = {}
    def tarai(x, y, z):
        if x <= y: return y
        key = x, y, z
        val = cache.get(key)
        if val is not None:
            return val
        val = tarai(
            tarai(x-1, y, z),
            tarai(y-1, z, x),
            tarai(z-1, x, y)
        )
        cache[key] = val
        return val
    return tarai

tarai = make_tarai()

with Timer():
    val = tarai(100, 50, 0)

print(val)